Boiler runs but does not heat the building adequately; radiators or air handlers are lukewarm.

Safety first: Use caution around hot pipes and components.

• Check setpoint and reset: Review the boiler's CH (central heat) setpoint and outdoor reset settings. Increase the target temperature slightly within Lochinvar's recommended range.
• Bleed air: Air in radiators or loops reduces heat transfer. Bleed radiators and high points until water flows steadily.
• Verify circulator speed: If using a multi-speed or ECM pump, ensure it is not set to the lowest speed. Adjust as appropriate for system design.
• Inspect thermostatic valves: Ensure thermostatic radiator valves or zone valves are open and not stuck closed.

Professional help: Persistent underheating may indicate incorrect boiler sizing or system design; consult a hydronic specialist.